1. Field of the Invention
The present invention relates to a driving circuit of a light emitting diode; in particular, to a driving circuit having the function of eliminating ghost phenomenon.
2. Description of Related Art
Light emitting diodes (LEDs) are small, power saving, and durable components. Along with the maturity of the manufacturing processes and cost reducing, more and more products are using light emitting diode as a light source. The light emitting diode is used in several kinds of equipments, such as headlight lamp of a vehicle, traffic light, word displayer, signboard, large screen video display, simple and building illumination, and LCD backlight.
Please refer to FIG. 1. FIG. 1 shows a schematic diagram of a conventional driving device of a light emitting diode. The driving device of the light emitting diode mainly includes a driving line selector 110 and a driving circuit 120. The driving line selector 110 may select the conducted driving lines L1 and L2. Every driving line L1 or L2 is connected with several respective light emitting diodes D1˜D4, as shown in FIG. 1. The driving circuit 120 is for controlling driving currents of the light emitting diodes D1˜D4, and has several current driving terminals OUT1 and OUT2 which correspond to different light emitting diodes D1˜D4. In detail, the driving circuit 120 has a current source circuit for controlling the currents flowing into the current driving terminals OUT1 and OUT2, in order to control the brightness of the light emitting diodes D1˜D4.
In the multi scanning driving structure, such as two scanning or four scanning, the driving line selector 110 must scan several sets of light emitting diodes in one single frame period. When the scanning processes are switching, a ghost phenomenon may occur because of the parasitic capacitance of the light emitting diodes, and the phenomenon may get worse due to the increase of the switch actions.